1. Field
The present invention relates generally to electric motor applications, and more specifically, to electric motor applications for electric powered vehicles.
2. Background
Recently, due to the shortage of gasoline and the ecological consequences of such use, various proposals have been created dealing with alternative power sources for motor vehicles. One of the most popular and promising proposals relates to electric powered vehicles. The difficulty encountered with electric powered vehicles, however, is the inability to deliver sufficient power for long-range operation without utilizing an extremely large number of heavy batteries. The electric motor driven cycle, on the other hand, is substantially lighter than the automobile, and therefore, tends to have significantly lower power requirements. As a result, electric motor driven cycles, such as motorcycles and mopeds, are ideal for electric power applications.
Whether the electric motor driven cycle is classified as a motorcycle or moped may have significant implications. A motorcycle, for example, requires that the driver has a special license and that the motorcycle be registered with the state. Mopeds, on the other hand, typically do not require that the driver have a license and does not require state registration. Therefore, it is commercially advantageous for a manufacturer to be able to classify the electric motor driven cycle as moped. The classification is often based on the maximum horsepower of the vehicle and is often different in each state. This presents a significant challenge to manufacturers seeking to achieve a standardized design.
A standardized design could be achieved by selecting a motor with the lowest horsepower rating of any state in the nation for a moped classification. The problem with this approach is that the performance of the electric motor driven cycle may be less than optimal in states where the horsepower rating for mopeds in substantially higher. Alternatively, the electric motor driven cycle may be designed to operate with different motors depending on the state in which the classification of the vehicle will be made. This approach will allow the electric motor driven cycle to operate at the maximum horsepower allowed by any particular state, but may result in various commercial disadvantages to the manufacturer in terms of inventory management, quality testing, maintenance, and the like.
Another consideration that may impact on the performance of the electric motor driven cycle designed for a moped classification is the manner in which the maximum horsepower is measured by the state. The state measures what is commonly referred to as the maximum brake-horsepower of the vehicle. This measurement can be made by applying a varying load to the drive wheel at full throttle and measuring the force applied by the drive wheel to the load at different speeds. The horsepower can then be computed by means well known in the art and plotted at different drive wheel speeds to generate a horsepower curve. The peak horsepower, which is the maximum brake-horsepower used by the state to classify the vehicle, can be determined from the horsepower curve. A typical horsepower curve looks like a parabola. Depending on certain parameters of the motor, the peak horsepower delivered by the motor may occur at the mid-point of the motor's operational RPM range. In limited horsepower applications, horsepower delivered below the peak drops and limits the starting power available to move the vehicle, and top speed is limited by load.
Accordingly, there is a need in the art for improvements in electric motor control technology that can deliver the maximum horsepower to the drive wheel under varying load conditions. This technology should be adaptive to comply with the maximum horsepower requirement of each state.